The Cardinal Rule states that all operations must expose the minimum number of ________ for the minimum amount of ________ to the minimum amount of ________ to be consistent with safe operations.

• A. Supervisors, hours, and equipment
• B. People, energy, and materials
• C. Workers, risk, and procedures
• D. People, time, and explosives

Answer: (D)

The safety idea being tested is that exposure to hazards should be kept as low as possible by trimming three factors: who is exposed, for how long they are exposed, and how much hazardous material is involved. The Cardinal Rule states you should expose the minimum number of people to the minimum amount of explosives for the minimum amount of time to be consistent with safe operations. This matters because fewer people in the hazard zone reduces the chance of injury, shorter exposure limits the window for an accident, and using less explosive minimizes potential energy and blast effects. In practice, you bring in only essential personnel, plan to minimize the time spent in danger zones, and use only the smallest effective quantity of explosives with proper safety controls. The other phrasings don’t capture this trio of exposure, duration, and material in the safety-critical context.